With the development of high integration and high speed semiconductor devices, wiring structure thereof is becoming finer and reduction of electrical capacitance between wirings is getting more and more important. To meet such technical requirements, an organic material of a low dielectric constant has been developed as a low-k film material for use in forming an interlayer insulating film. Since, however, the low-k film material dose not have sufficient mechanical strength required as the interlayer insulating film, there have been recently suggested various methods for enhancing the mechanical strength of the organic material film by using electron beams. For example, disclosed in Japanese Patent Laid-open Publication No. 2000-221699 (paragraphs [0015], [0016] and [0020]) is a curing method for improving a film quality of an organic material film such as a resist film or an antireflection film by facilitating a carbonization reaction by way of irradiating electron beams thereto in oxidizing or reducing atmosphere. Further, U.S. Pat. No. 6,652,922 discloses another curing method for hardening an organic material by way of irradiating electron beams thereto in the presence of oxygen (O2), argon (Ar), nitrogen (N2), helium (He) or a combination thereof, thereby improving a heat resistance or a plasma resistance of the organic material film of a low dielectric constant.
Though such curing methods serve to improve mechanical strength of the organic material film by hardening a surface region thereof through the use of electron beams, there remain certain problems in that the k value at the surface region of the organic material film may be deteriorated or methyl groups may be decomposed, to thereby reduce a chemical resistance thereof during a cleaning process, for example.